不同土壤水分条件下施氮对甘薯干物质积累及块根品质的影响

摘要

To explore the effect of nitrogen application on dry matter accumulations and qualities of tuberous roots of sweet potato (Sushu 14) under different soil moistures conditions,a pot experiment was conducted in plastic-covered greenhouse with three soil moistures (40％,80％ and 120％) and two nitrogen application levels (no nitrogen fertilizer as control,and 150 mg nitrogen in 1 kg air-dried soil).The results showed that increasing soil moisture was beneficial to the dry matter accumulation of sweet potato.The application of nitrogen fertilizer improved the shoot dry matter of sweet potato under all three soil moistures conditions.Nitrogen application lowered dry matter accumulation in tuberous root at low soil moisture level,and increased it at high soil moisture level,indicating that sufficient nutrients and water resource were necessary for high production of sweet potato.Increasing moisture reduced the content of vitamine C and raised soluble sugar content and related components.Hower,after nitrogen application,the down trend of vitamin C became gentle,and the contents of soluble sugar came down,resulting in the edible quality decline.The response of starchs content to soil moisture was related to nitrogen application level.Under no nitrogen application condition,the contents of amylose,amylopectin,total starch and ratio of amylase to amylopectin decreased with the rise of soil moisture.After nitrogen application,the amylose content and ratio of amylase to amylopectin decreased under low soil moisture condition,and the contents of amylase,amylopectin and total starch were remarkably increased under high soil moisture condition,resulted in the improvement of processing quality.In conclusion,both soil moisture and nitrogen application played important roles in sweet potato qualities and yield,and should be taken into consideration during potato cultivation in order to achieve high quality and yield.%为研究不同土壤水分条件下施用氮肥对甘薯干物质积累及块根品质的影响,以苏薯14为试验材料,设置盆栽土培试验,设3个土壤含水量(田间持水量40％、80％和120％)和2个施氮水平[1 kg风干土施0mgN(对照)、150 mg N].试验结果表明:(1)提高土壤含水量有利于甘薯干物质积累,施氮可提高甘薯藤蔓干物质积累量;施氮在土壤含水量较低时会降低块根干物质积累量,含水量较高时会促进块根干物质积累,表明充足的养分和水分是充分发挥甘薯高产潜能的必需条件.(2)提高土壤含水量降低块根维生素C含量,提高可溶性糖及其主要组分含量;施氮后,随土壤含水量增大块根维生素C含量降幅减小,可溶性糖及其主要组分含量也显著降低,导致食用品质降低;土壤含水量对块根淀粉含量的影响程度与施氮有关.不施氮时,直链淀粉、支链淀粉、总淀粉含量以及直/支比率均随土壤含水量提高而降低,施氮后,在土壤含水量较低时块根直链淀粉含量和直/支比率显著降低,而在土壤含水量较高时块根直链淀粉、支链淀粉和总淀粉含量显著提高,由此加工品质提高.可见,土壤水分和氮素对甘薯产量和品质均有重要作用,为获得高产优质甘薯,应在种植过程中综合考虑实际土壤水分条件和施肥水平.